1. Field of the Invention
The present invention relates to an apparatus for sorting and stacking sheet materials emitted from an image forming apparatus such as copier, duplicator or other recording apparatus, and more particularly to an improvement in an apparatus (hereinafter referred to as sorter) for efficiently sorting and storing sheet materials such as copy paper or recording paper (hereinafter referred to as sheets) into plural storing places according to the content of the record on such sheets.
2. Description of the Prior Art
With the progressive increase in the processing speed of image forming apparatus in recent years, it has become customary to use a sorter for automatic sorting of processed sheets in combination with such image forming apparatus in order to achieve an improved work efficiency. In such high-speed apparatus, however, the protection of the sheets in transportation and the apparatus itself in case of erroneous operation such as sheet jamming during transportation thereof is more important but more difficult to achieve.
In a combined system consisting of such image forming apparatus and a sorter, such sheet jamming may occur in the apparatus or in the sorter, and, in case of the jamming in the apparatus, the sorter may continue its function until all the sheets in transportation are sorted into appropriate trays, while in case of the jamming in the sorter, the sheet transportation in the sorter has to be interrupted immediately. In such case, however, the sheet transportation in the image forming apparatus has to be continued until all the sheet already in process in said apparatus are emitted therefrom in order to avoid undesirable effect for example by the heat source for image fixing, and for this reason the sorter has to be provided with suitable means for receiving such sheets to be emitted from the image forming apparatus. For this purpose there is already known to provide a tray for temporarily receiving the processed sheets between the image forming apparatus and the sorter or on either thereof and to activate diverting means in case of a sheet jamming thereby guiding the sheets into such emergency tray through a separate diverting path. Such conventional method is however defective in that the presence of the abovementioned emergency tray and the associated diverting means and diverting path requires a significant additional space just for an emergency case, thus increasing the volume of the entire system, and necessitates the inspection of said tray in case of jamming in addition to the ordinary transportation path, thus complicating the operation procedure and delaying the restart of normal operation.
Also the convention sorter is generally equipped with sheet transporting means for driving the sheets into appropriate trays composed of driven or idler rollers positioned at the respective entrances of sheet stacking trays and a group of rollers and/or belts engaging with the abovementioned rollers, and sheet diverting means functioning independently from said sheet transporting means and guiding each sheet to a determined tray. The sorter of such structure is however defective in that the various components have to be of a limited shaft diameter in order to avoid mutual interference between the sheet diverting means and the rollers and belts constituting the sheet transporting means which have to be positioned in a quite limited space, and that the sheet guide members performing auxiliary function in the sheet transporting means can only be employed in limited positions. For this reason such sorter is inevitably associated with a major drawback of structural uncertainty in the mutual positional relationship between the sheet transporting means and the diverting means, which can only be prevented at the sacrifice of the increase of entire volume of the sorter or of the reduction in the number of trays. Another drawback of such sorter lies in that the sheet is often not properly placed on the tray or on the stack of sheets already placed in the tray, which is called sheet end remaining phenomenon, because the sheet, in the transport into a determined tray by the activated diverting means, is merely guided between the diverting means and the roller positioned at the entrance of tray without active driving force after the release of the trailing end of the sheet from the sheet transporting means and is subjected to a curving action, thus developing a curl on said trailing end.